The reliability of the a-Si drum has been investigated via environmental tests and durability copy testing, and its electrophotographic properties have been confirmed to be very stable. Regarding imaging properties, a-SiC surface layer plays an important part suppressing the noise within the image. It has been discovered that the blurring of the image in high humidity after many copying cycles is caused by the deterioration of the surface layer which occurs through exposure to corona discharge. This blurring is eliminated by preventing absorption of moisture at the surface, such as heating the drum. In this manner, it has been observed that a-Si drum maintains a high quality image up to 1,000,000 copy sheets.